xfs: ask the dentry cache if it knows the parent of a directory

It's possible that the dentry cache can tell us the parent of a
directory.  Therefore, when repairing directory dot dot entries, query
the dcache as a last resort before scanning the entire filesystem.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

4 files changed, 74 insertions, 0 deletions

diff --git a/fs/xfs/scrub/dir_repair.c b/fs/xfs/scrub/dir_repair.c
index cf3b03d902f5..e209c04f5c39 100644
--- a/fs/xfs/scrub/dir_repair.c
+++ b/fs/xfs/scrub/dir_repair.c
@@ -1110,6 +1110,29 @@ xrep_directory_scan_parent(
 	return parent_ino;
 }
 
+/*
+ * Look up '..' in the dentry cache and confirm that it's really the parent.
+ * Returns NULLFSINO if the dcache misses or if the hit is implausible.
+ */
+static inline xfs_ino_t
+xrep_directory_dcache_parent(
+	struct xrep_dir		*rd)
+{
+	struct xfs_scrub	*sc = rd->sc;
+	xfs_ino_t		parent_ino;
+	int			error;
+
+	parent_ino = xrep_parent_from_dcache(sc);
+	if (parent_ino == NULLFSINO)
+		return parent_ino;
+
+	error = xrep_parent_confirm(sc, &parent_ino);
+	if (error)
+		return NULLFSINO;
+
+	return parent_ino;
+}
+
 /* Try to find the parent of the directory being repaired. */
 STATIC int
 xrep_directory_find_parent(
@@ -1119,6 +1142,10 @@ xrep_directory_find_parent(
 	if (rd->parent_ino != NULLFSINO)
 		return 0;
 
+	rd->parent_ino = xrep_directory_dcache_parent(rd);
+	if (rd->parent_ino != NULLFSINO)
+		return 0;
+
 	rd->parent_ino = xrep_directory_lookup_parent(rd);
 	if (rd->parent_ino != NULLFSINO)
 		return 0;
diff --git a/fs/xfs/scrub/parent.h b/fs/xfs/scrub/parent.h
index 10612f204d41..03681ab24596 100644
--- a/fs/xfs/scrub/parent.h
+++ b/fs/xfs/scrub/parent.h
@@ -10,5 +10,6 @@ int xchk_parent_lock_two_dirs(struct xfs_scrub *sc, struct xfs_inode *dp);
 
 int xrep_parent_confirm(struct xfs_scrub *sc, xfs_ino_t *parent_ino);
 int xrep_parent_scan(struct xfs_scrub *sc, xfs_ino_t *parent_ino);
+xfs_ino_t xrep_parent_from_dcache(struct xfs_scrub *sc);
 
 #endif /* __XFS_SCRUB_PARENT_H__ */
diff --git a/fs/xfs/scrub/parent_repair.c b/fs/xfs/scrub/parent_repair.c
index e8c1d759259e..648345b1c1a9 100644
--- a/fs/xfs/scrub/parent_repair.c
+++ b/fs/xfs/scrub/parent_repair.c
@@ -282,6 +282,44 @@ out_rele:
 	return error;
 }
 
+/* Check the dentry cache to see if knows of a parent for the scrub target. */
+xfs_ino_t
+xrep_parent_from_dcache(
+	struct xfs_scrub	*sc)
+{
+	struct inode		*pip = NULL;
+	struct dentry		*dentry, *parent;
+	xfs_ino_t		ret = NULLFSINO;
+
+	dentry = d_find_alias(VFS_I(sc->ip));
+	if (!dentry)
+		goto out;
+
+	parent = dget_parent(dentry);
+	if (!parent)
+		goto out_dput;
+
+	if (parent->d_sb != sc->ip->i_mount->m_super) {
+		dput(parent);
+		goto out_dput;
+	}
+
+	pip = igrab(d_inode(parent));
+	dput(parent);
+
+	if (S_ISDIR(pip->i_mode)) {
+		trace_xrep_findparent_from_dcache(sc->ip, XFS_I(pip)->i_ino);
+		ret = XFS_I(pip)->i_ino;
+	}
+
+	xfs_irele(XFS_I(pip));
+
+out_dput:
+	dput(dentry);
+out:
+	return ret;
+}
+
 /*
  * Scan the entire filesystem looking for a parent inode.
  *
@@ -384,6 +422,12 @@ xrep_parent(
 	if (sick & XFS_SICK_INO_DIR)
 		return -EFSCORRUPTED;
 
+	/* Does the VFS dcache have an answer for us? */
+	parent_ino = xrep_parent_from_dcache(sc);
+	error = xrep_parent_confirm(sc, &parent_ino);
+	if (!error && parent_ino != NULLFSINO)
+		goto reset_parent;
+
 	/* Scan the entire filesystem for a parent. */
 	error = xrep_parent_scan(sc, &parent_ino);
 	if (error)
@@ -391,6 +435,7 @@ xrep_parent(
 	if (parent_ino == NULLFSINO)
 		return -EFSCORRUPTED;
 
+reset_parent:
 	/* If the '..' entry is already set to the parent inode, we're done. */
 	curr_parent = xrep_dotdot_lookup(sc);
 	if (curr_parent != NULLFSINO && curr_parent == parent_ino)
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 3151985d9fbe..476fb62a6e54 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -1871,6 +1871,7 @@ DEFINE_EVENT(xrep_parent_salvage_class, name, \
 DEFINE_XREP_PARENT_SALVAGE_CLASS(xrep_directory_salvaged_parent);
 DEFINE_XREP_PARENT_SALVAGE_CLASS(xrep_dir_salvaged_parent);
 DEFINE_XREP_PARENT_SALVAGE_CLASS(xrep_findparent_dirent);
+DEFINE_XREP_PARENT_SALVAGE_CLASS(xrep_findparent_from_dcache);
 
 #endif /* IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR) */